1. Field of the Invention
The invention relates to a percussion apparatus according to the preamble of patent claim 1. The invention relates in particular to a percussion apparatus which can be used in an impact hammer and/or drill hammer.
When work is done using impact and drill hammers, the situation often arises where the tool, e.g. a cutter or a bit, wedges or jams in the rock. While a practiced operator can usually still prevent the tool from jamming during drilling with the drill hammer, it is not always possible, during demolition work using a large impact hammer, even for the expert to avoid wedging or jamming of the cutter. It is usually difficult to release a wedged tool because this can only be accomplished by using a second cutter, in the case of a certain hammer design only by using a second hammer, to release the jammed tool by impact. During the impact-release of a jammed bit, the effort necessary for this purpose is usually particularly high since the drill is already lodged deep in the rock and it is thus necessary to cut away all the rock around the drill hole. In any case, the impact-release of a jammed tool requires considerable outlay in terms of time and equipment.
2. Description of the Related Art
U.S. Pat. No. 5,485,887 discloses a percussion apparatus having an impact-generating device which has an axially reciprocating percussion piston. In an operating state, a tool can be forced in an operational-impact direction by the percussion piston while, in an impact-release state, a blow of the percussion piston can be transmitted to the tool such that said tool can be forced in an impact-release direction, which is counter to the operational-impact direction. The reversal of the impact direction is achieved purely pneumatically by the displacement of an outer piston, which encloses the percussion piston.